This application claims the priority of German Application 299 19 920.7 filed Nov. 12, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a stereotactic frame having a ring which, for a radiological treatment in the head area, can be supported under pressure on a patient""s skull bone by several posts fastened on the ring.
For the radiosurgical treatment, particularly of tumors and other small lesions in the head area, it is known to aim several high-energy radiation sources, particularly gamma radiation sources (Cobalt 60 sources), which are arranged in a helmet, at a radiation center. The tumor to be treated or the lesion to be treated is arranged in this radiation center. This takes place by way of the stereotactic frame, such as a Leksell frame, which is supported on the patient""s skull bone and establishes the geometrical reference to the radiation sources.
For the above purpose, the stereotactic frame is clamped to the patient""s skull bone by at least one positioning screw, which is provided on one of the posts. During the therapeutic treatment, it is necessary to carry out several adjustments in which the position of the patient""s head is changed with respect to the radiation sources. In this case, the danger exists that the ring of the stereotactic frame becomes loose, whereby the geometrical reference between the positions of the radiation sources or of the radiation center at which the radiation sources are aimed, and an accurate position of the patient""s head will be lost. This results in the risk that the diseased zone in the head area, for example, in the brain, will no longer be irradiated but adjacent healthy and possibly vital tissue. This risk occurs particularly if the adjustments of the patient""s head take place automatically.
An object of the present invention is, therefore, to provide a stereotactic frame in which a loosening of the stereotactic ring can be determined.
According to the invention, this object has been achieved by providing a measuring device on at least one post. This measuring device measures the material deformation of the post which results from the pressure or tension which supports the stereotactic frame on the skull bone.
In this manner, it is possible to measure the stressing of the stereotactic ring or frame and to determine a change of this stress or a relief and to display a corresponding alarm signal. The present invention is based on the recognition that, during the fastening of the stereotactic frame, relatively high forces act upon certain construction elements of the frame. These forces result in measurable material deformations which can be determined, for example, by wire strain gauges and equally acting measuring elements.
Wire strain gauges are preferably used because they are not susceptible to radioactive radiation and can therefore be used in radiation fields. One measuring device respectively, particularly wire strain gauges, are preferably used on two posts. A loosening of the stereotactic ring causes a clear change of the measuring signal which can be determined and displayed in an analyzing unit connected to the measuring device.